The present invention relates to an oil recovery process utilizing electrical means, and more particularly to a process wherein an electrical potential gradient is established across an oil-bearing formation to enhance oil recovery.
It is well documented that the flow of fluids through porous media results when a directional potential is applied across the media containing the fluids. This fluid flow, known as the electroosmotic effect, is due to electrically charged layers of opposite signs at the boundary between the fluid and porous media. See for example Textbook of Physical Chemistry, Second Edition, S. Glasstone, MacMillan and Co. Ltd., 1948, page 1219.
Processes utilizing the transfer of reservoir fluids by electroosmosis are described in, for example, U.S. Pat. Nos. 3,642,066 to Gill, and 2,799,641 to Bell. These and other prior art processes have been concerned with increasing the fluid flow within the formation toward a production well. To that end, the polarity of the electrode means in an injection and production well has, by convention, been positive and negative respectively, in order to assist fluid flow.
It is also known in the prior art to dewater an oil-bearing formation by applying a potential field between an anode and a cathode within an injection or production well. For instance, in the process set forth in U.S. Pat. No. 3,417,823 to Faris, a drainage area is set up around the cathode to collect water away from a production zone.
In a number of experiments performed by the inventor following the prior art teachings at least two adverse effects were noted in the recovery, which effects have not been well documented in the literature. The experiments involved injecting hot displacement fluids through an injection well into an oil sand-packed tube while maintaining a unidirectional potential positive to negative between spaced injection and production wells respectively. The effects noted were, firstly, there was an early breakthrough of water at the production well, and secondly, the oil to water ratio of the produced fluids rapidly decreased on continued production.